| 摘要 |
PURPOSE:To identify surely a network control signal by grasping a sequence of transmission control, identifying a non-signal period in the transmission of the network control signal and detecting and deciding a reception signal during the period. CONSTITUTION:A signal from a network is given to a demodulator 20 and to a binary-coding circuit 22 through a reception line 10, a buffer amplifier 12, a band pass filter (BPF)14, VSB inverse filter 16 and an automatic gain control circuit (AGC)18. A control signal generating circuit 32 receives a binary-coding signal from the binary-coding circuit 22 and outputs respectively a gate signal to a lead 42, a clear signal to a lead 40 and a data-in ready signal to a lead 48 respectively in the timing shown in Figs. C, D and E. A reference clock generator 34 generates a reference clock of a prescribed frequency sufficiently higher than that of a reception signal to be detected and it is outputted to the lead 44. An AND gate 36 outputs a reference clock to an output 46 during a significant period of the gate signal only outputted to the lead 42 from the control signal generating circuit 32. Thus, a counter circuit 48 counts the clock of the outputs 46 of the AND gate 46 and stores the count value.
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